Fig. 4 Model of nitrogen fixation response to manganese and ureide accumulation during water deficit. In the absence of sufficient manganese, ureide breakdown is impaired, leading to an accumulation of leaf ureides. An increase in leaf ureides results in the export of ureides from leaves to nodules, along with water and sugars carried in phloem. Increased ureide concentration in nodules inhibits N₂ fixation, lessens nodule respiration and sink strength, and decreases flux of water to nodules

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